MATLAB: How to take out specific month from data

sir i have 95 year daily model output rainfall data form 2006-1-1 to 2100-12-31.i want to take out nov to feb which include leap years. i have program for this.this is working perfectly for who does not include leap year but i want to include leap years then please suggest me what will change in this program for this. in between 2006 to 2100 have 24 leap years but my data include only 23 leap years,this is not not include end(last) leap year. this is daily data.sir my precipitaion data size is ( 20x22x34698) (lat,lon.time) for india region.sir please help me. this is include leap years.please help me.thank you

dten = datenum([2006 1 1 ;2100 12 31])

[~,M] = datevec(dten(1):dten(2));

xx = find(ismember(M,[11 12 1 2]));

[m,n,k] = size(prec_all_years1);

ii = cumsum(eomday(2014,1:12));

x0 = rem(0:k-1,365)+1;

xx_logic = x0 <= ii(2) | x0 > ii(10);

p = prec_all_years1(:,:,xx_logic);

max_rainfall = max(reshape(p,m*n,[]));

Best Answer

As noted above, you were already there--

dten = datenum([2006 1 1 ;2100 12 31]);   
[~,M] = datevec(dten(1):dten(2));
p = prec_all_years1(:,:,ismember(M,[11 12 1 2]));

IOW, just throw away all the leap year stuff if don't want it. But if want to go back, the preceding logical vector is much simpler way to select/not select those years than the initial logic.

[Y,M] = datevec(dten(1):dten(2));
p = prec_all_years1(:,:,ismember(M,[11 12 1 2]) & ~(eomday(Y,2)==29));

will select Nov-Feb for the non-leap years in the range of years Y

Look up Using Logicals in Array Indexing in the documentation for more details.

Related Solutions

MATLAB: Convert “number of days since” to datetime, given 365-day and 360-day calendars (not Gregorian)

Adding support for a broader range of calendars is something I've been thinking about. For a fixed-length calendar (360-day or 365-day), there are a couple issues to deal with:

1) Where do you put the extra days in the Gregorian calendar? Is day 59 from the model on a leap year 29 Feb or 1 Mar? If 29 Feb, then the extra day falls at the end of the year.

2) How do you want to fill in data for the days that aren't represented in the model data? Fill with previous? average of the previous and next? Leave it as missing? This matters when you want to do more aggregation/statistics on your data (e.g. monthly mean and standard deviation).

3) If you're using fraction-of-year values (second column of var_time_mx), you run into floating point and roundoff issues and needing to correct things to the nearest day.

One approach that I've come up with:

t = readtable('var_time_mx.txt');
d = t.Var1;
dt = datetime(1949,12,1)+calyears(fix(d/365))+caldays(floor(mod(d,365)))+hours((mod(d,365)-floor(mod(d,365)))*24)

This approach includes 29 Feb 1952, but skips 30 Nov 1952 (because 1 Dec is the start of the 365-day year in your definition). This is a bit weird, but a pain to work around and may not be necessary for your use. If it is, you can us the leapyear() function to check whether the dates need to be shifted by one day.

MATLAB: How to take out specific month from data

Let the 'a' is date for first frame of your 3D matrix (eg 'prec_all_years')

a = [2006,1,1];
[m,n,k] = size(prec_all_years1);
dten = datenum([2006 1 1 ;2100 1 1])
[~,M] = datevec(datenum(a) + (0:k-1)');
xx = ismember(M,[11 12 1 2]);
p = prec_all_years1(:,:,xx);
max_rainfall = max(reshape(p,m*n,[]));

add

[m,n,k] = size(prec_all_years1);
ii = cumsum(eomday(2014,1:12));
x0 = rem(0:k-1,365)+1;
xx_logic = x0 <= ii(2) | x0 > ii(10);
p = prec_all_years1(:,:,xx_logic);
max_rainfall = max(reshape(p,m*n,[]));

Best Answer

Related Solutions

MATLAB: Convert “number of days since” to datetime, given 365-day and 360-day calendars (not Gregorian)

MATLAB: How to take out specific month from data

Related Question